1. Field of the Invention
The present invention relates to a lithium titanium oxide (LTO)/carbon composite, a preparation method for the LTO/carbon composite, a negative electrode material using the LTO/carbon composite, and a hybrid super capacitor using the negative electrode material. More particularly, the present invention relates to a lithium titanium oxide (LTO)/carbon composite, a preparation method for the LTO/carbon composite, a negative electrode material using the LTO/carbon composite, and a hybrid super capacitor using the negative electrode material, where the LTO/carbon composite is formed to insert a carbon-based additive into a plurality of voids formed in the LTO granules, thereby improving the electrical conductivity.
2. Description of the Related Art
A hybrid super capacitor or a lithium secondary battery contains lithium titanium oxide (LTO) having a spinel structure, which is structurally stable, as a negative electrode material. The LTO advantageously has a high cycle property due to its zero-stain characteristic that almost no volume expansion occurs during the charging/discharging process. Hence, the LTO can be used as a negative electrode material required to have high output and long life span.
Korean Laid-Open Patent No. 2011 0013460 relates to a preparation method for LTO, which includes the steps of mixing a lithium carbonate powder or a lithium hydroxide powder with a titanium oxide used as a precursor for firing; using a compound containing titanium and lithium from a solution containing both titanium and lithium components as a precursor for firing; preparing a mixed slurry of a titanium compound powder and a lithium-containing compound; depositing the lithium compound through spray drying to prepare a mixture of the titanium compound powder and the lithium compound; and using the mixture as a precursor for firing.
The conventional LTO prepared as described in the Korean Laid-Open Patent No. 2011 0013460 is hard of high-speed charging/discharging because of its low electronic conductivity and disadvantageously has a low theoretical capacity of about 175 mAh/g. Further, electrodes using the conventional LTO tend to have a resistance increasing with an increase in the thickness. Thus, there is a need of performing a process for preparing a thin film to prevent this problem. This can lead to deterioration in the productivity for the product.